Printers include those printers, such as inkjet printers, having a paper-feed roller which rotates (indexes) to a desired rotational position to advance a paper (or other type of print medium) sheet, such as to advance a paper sheet between print swaths printed by a print head mounted on a carrier system. In a known design, a DC (direct current) motor is used to drive the paper-feed roller. An output signal, such as a PWM (pulse-width-modulated) output voltage signal, from a paper-feed controller, such as a proportional or a PI (proportional integral) or a PID (proportional integral derivative) controller, is used to control the motor. Typically, the controller is used in a feedback control system wherein an encoder measures the actual rotational position of the paper-feed roller and wherein the error signal between the actual rotational position (measured by the encoder) and the desired rotational position is used as the input to the controller.
In one known mode of operation, once the paper-feed roller reaches the desired rotational position, the controller shuts the motor off. However, in this one mode, the quick release of the trapped energy in the gear train and the motor tends to roll back the paper-feed roller away from its desired rotational position.
In another known mode of operation, the controller remains active even after the paper-feed roller reaches the desired rotational position. However, in this other mode, there is a large amount of processor overhead in continuing feedback control while printing. Also, in this other mode, it is difficult to filter out roller feedback caused by carrier vibrations, wherein such feedback tends to be amplified by the paper-feed controller.
What is needed is an improved method for rotating a printer paper-feed roller.